Female Sprague-Dawley rats will be implanted with chronic EEG and EMG electrodes and with permanent cannulas into the jugular vein for drug administration. Using these experimental animals, the proposed work will assess the degree and duration of antagonism of the CNS effects of morphine following acute and chronic treatment with naloxone and naltrexone. This will be accomplished by quantifying EEG and behavioral changes that vary as a function of experimental manipulations. The proposed work will also assess the comparative development of tolerance and the degree of cross-tolerance to morphine, methadone, and LAAM in rats dependent on these narcotics, respectively. Here also associated changes in EEG parameters and behavior will be quantified. In other experiments we will further delineate the characteristics of EEG Power spectra associated with "drug-seeking" behavior in rats self-administrating morphine, methadone, or LAAM. BIBLIOGRAPHIC REFERENCES: Moreton, J.E., Roehrs, T. and Khazan, N.: Drug self-administration and sleep-awake activity in rats dependent on morphine, methadone or l-alpha-acetylmethadol. Psychopharmacology 47: 237-241, 1976. Young, G.A., Moreton, J.E., and Khazan, N.: Duration of action of naloxone subcutaneous pellets in antagonizing the EEG and operant behavioral effects of morphine in the rat. J. Pharm. Pharmacol. 28:658-660, 1976.